This invention relates generally to drains and apparatus for priming a siphon and particularly to a temperature actuated apparatus which utilizes solar energy to fill the siphon. An apparatus of this general type is shown and described in U.S. patent application Ser. No. 714,867 now U.S. Pat. No. 4,059,126, of Malcolm Horace Nickerson which is assigned to the assignee of this application. The container having the heating and cooling chamber of the prior application has one valve for exhausting air at above atmospheric pressure from the chamber during heating of the air in the chamber and a check valve in communication with the siphon for containing above atmospheric pressure in the chamber. These valves are in addition to the valve at the outlet of the siphon. During operation the amount of subatmospheric pressure in the chamber increases as a result of temperature changes and exposure to the sun which makes it necessary to construct the container surrounding the chamber with sufficient strength to withstand the forces resulting from the increased subatmospheric pressure and thereby prevent collapse of the container.